can1357/oh-my-pi · error · SeqError

format string may not be specified when printing equal width

Error message

format string may not be specified when printing equal width strings

What it means

This is the `FormatAndEqualWidth` variant of the seq error enum. GNU seq's `--equal-width` (`-w`) pads all numbers to equal width, which is incompatible with a user-supplied `--format` (`-f`) string, since the format already dictates output width. The library rejects the mutually exclusive combination up front.

Source

Thrown at crates/pi-builtins/src/seq.rs:448

	///
	/// The parameters are the [`String`] argument as read from the
	/// command line and the underlying parsing error itself.
	#[error("invalid {} argument: {}", parse_error_type(.1), .0.quote())]
	ParseError(String, ParseNumberError),

	/// The increment argument was zero, which is not allowed.
	///
	/// The parameter is the increment argument as a [`String`] as read
	/// from the command line.
	#[error("invalid Zero increment value: {}", .0.quote())]
	ZeroIncrement(String),

	/// No arguments were passed to this function, 1 or more is required
	#[error("missing operand")]
	NoArguments,

	/// Both a format and equal width where passed to seq
	#[error("format string may not be specified when printing equal width strings")]
	FormatAndEqualWidth,
}

fn parse_error_type(e: &ParseNumberError) -> &'static str {
	match e {
		ParseNumberError::Float => "floating point",
		ParseNumberError::Nan => "'not-a-number'",
	}
}

}

use self::{error::SeqError, number::PreciseNumber};

const OPT_SEPARATOR: &str = "separator";
const OPT_TERMINATOR: &str = "terminator";
const OPT_EQUAL_WIDTH: &str = "equal-width";
const OPT_FORMAT: &str = "format";

View on GitHub (pinned to 9690622007)

Solutions

1. Remove the `--equal-width`/`-w` flag if you need a custom format.
2. Remove the `--format`/`-f` string if you need equal-width padding; `-w` alone pads with the default format.
3. Achieve custom formatting plus padding entirely in the format string, e.g. `-f '%3.0f'`.
4. If options come from config/variables, make them mutually exclusive in your argument assembly logic.

Example fix

// before
seq -f '%3.0f' -w 1 5

// after
seq -f '%3.0f' 1 5

let uses_format = args.iter().any(|a| a == "-f" || a == "--format");
let uses_equal_width = args.iter().any(|a| a == "-w" || a == "--equal-width");
if uses_format && uses_equal_width {
    eprintln!("seq: -f and -w are mutually exclusive");
    std::process::exit(2);
}

match seq_result {
    Err(SeqError::FormatAndEqualWidth) => eprintln!("drop either -f or -w; they cannot be combined"),
    Err(e) => eprintln!("seq: {e}"),
    Ok(out) => print!("{out}"),
}

When it happens

Trigger: Invoking the seq builtin with both a format string argument and the equal-width flag, e.g. `seq -f '%3.0f' -w 1 5`.

Common situations: Copy-pasted command lines where `-f` and `-w` accumulate from different option sources, or a user misunderstanding that `-w` and `-f` overlap in controlling output formatting.

Related errors

• missing operand
• unknown function: {0}
• unknown key binding function: {0}
• unimplemented: {0}
• I/O error occurred

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/f316b510b357e3fc. Report an issue: GitHub.